It's honestly mind boggling. Either they flat out don't understand the "rules" of the road or they're completely oblivious to the logjam of cars behind them. Or...they're just dicks.
Same thing drives me nuts on Independence Pass. Sure, it's a one lane highway, and for many, it can be scary, but there are so many opportunities to pull over and let people pass that don't want to drive like pansies
. Also because it's difficult to pass them if the cars in between you aren't making a move.
Blows my mind how people can see a line of cars behind them and not think, "huh, maybe I'm holding these guys up and should do something about it".